Rooms or enclosures shielded against electromagnetic radiation are in common use for RF emission testing equipment and other electronic testing.
Such shielded rooms are specially made enclosures and are of sufficient size to permit workmen to conduct various operations therein. The rooms must be provided with an opening of sufficient size to permit passage of workmen and equipment therethrough. A primary problem in the construction of such shielded enclosures is to provide a door which will completely seal the opening against electromagnetic radiation.
The shielded rooms and doors must be constructed of a metal which will afford protection against electromagnetic radiation.
In the prior art there have been serious problems associated with the design and construction of shielded doors as indicated in the following. The seals have not been effective because of gaps between the seal and the door. The reliability of the seals is poor due to fragile construction and thus will not stand extended usage.
The prior art doors utilizing integral expander tubes have been heavy, costly, complex, and subject to considerable maintenance. These doors have been inordinately thick so as to cause excessive vehicular and personal traffic problems caused by the inherently large gap in which the door slides. Where the doors are supplied with integral expander tubes they also must be supplied with compressed air lines to the door and thus require the moving of the air hoses along therewith.
The weight of the heavy doors causes considerable difficulty in manual operation that results in safety hazards.
An example of a relatively heavy, wide door having integral expander tubes is illustrated in U.S. Pat. No. 3,518,355 to Luce.
Another type of door having integral expander tubes between the door and frame is illustrated in U.S. Pat. No. 2,757,225 to Dunn. Here, the expander tubes are secured in recesses extending around the door edges. This type of arrangement is made to function only on hinged doors.
Three other prior art, United States Letters Patents deemed not to be pertinent to the present invention are No. 3,236,935 to Patton; No. 3,009,984 to Lindgren; and No. 3,256,384.